1. Field of the Invention
The present invention relates to an organic light-emitting diode display device, and more particularly, to the structure of an organic light-emitting diode display device for suppressing a vertical crosstalk phenomenon in the organic light-emitting diode display device having an internal compensation structure for threshold voltage variations in driving transistors.
2. Description of the Related Art
Flat panel display devices proposed for replacing the existing cathode ray tube display devices may include liquid crystal displays, field emission displays, plasma display panels, organic light-emitting diode (OLED) displays, and the like.
Of the types proposed, organic light-emitting diodes may provide advantages such as high brightness and low operation voltage characteristics, and a high contrast ratio because of being operated as a self luminous type that spontaneously emits light, and allowing the implementation of an ultra-thin display. Furthermore, the organic light-emitting diodes have characteristics such as facilitating the implementation of moving images with a response time of several microseconds (μs), having no limitation in viewing angle, and having stability, even at low temperatures.
FIG. 1 is a view illustrating an equivalent circuit diagram of one pixel in an organic light-emitting diode display device in the related art.
As illustrated in the drawing, in the organic light-emitting diode display device, a scan signal (Scan) line and a data signal (Vdata) line are formed in a crossed manner with each other, and a line for supplying a power voltage (VDD) is formed to be separated from the data signal (Vdata) line by a predetermined distance to form one pixel (PX).
Furthermore, the organic light-emitting diode display device may include a switching thin-film transistor (SWT) for applying the data signal (Vdata) to a first node (Ni) in response to the scan signal (Scan), and a driving thin-film transistor (DT) for receiving the driving voltage (VDD) at the source electrode and applying a drain current to the organic light-emitting diode (EL) according to a voltage applied to the first node (N1), and a capacitor (C1) for maintaining a voltage applied to a gate electrode of the driving thin-film transistor (DT) for a period of one frame.
Furthermore, the organic light-emitting diode (EL) may include an organic light-emitting layer formed between the cathode electrode and anode electrode, the anode electrode being connected to the drain electrode of the driving thin-film transistor (DT), and the cathode electrode being grounded (VSS). The organic light-emitting layer may include a hole transporting layer, an light emitting layer, and an electron transporting layer.
The foregoing organic light-emitting diode display device controls a current amount flowing through the organic light-emitting diode (EL) to display the gradation of an image, and the image quality is determined by the characteristics of the driving thin-film transistor (DT).
However, a threshold voltage variation between the driving thin-film transistors of different pixels may occur, even within one display panel, and a current flowing through each organic light-emitting diode (EL) may be changed, thereby causing a problem in which the desired gradation cannot be implemented. In order to address this problem, an internal compensation type pixel structure in which one or more sampling thin-film transistors (T1, T2) and a plurality of capacitors (C1, C2) for applying a reference voltage (VREF) are added, as illustrated in FIG. 2, to compensate a threshold voltage variation by sensing the threshold voltage of the driving thin-film transistor (DT) and removing a threshold voltage component sensed on the drain current of the driving thin-film transistor (DT) has been proposed.
However, the foregoing internal compensation type pixel structure requires that a larger number of thin-film transistors are provided compared to the related art FIG. 1, and therefore it has a disadvantage of reducing the aperture ratio.
Furthermore, the pixel may be designed in such a manner that the maximum aperture ratio can be secured in a limited pixel space, and therefore, a line connected to the gate electrode of the driving thin-film transistor (DT) is disposed adjacent to the data line (DL), and a voltage applied to the gate electrode is fluctuated due to the effect of coupling caused by a voltage change of the data line (DL) according to the parasitic capacitance, thereby varying the gate voltage of the driving thin-film transistor. It may change the drain current of the driving thin-film transistors, thereby causing image quality deterioration such as a vertical crosstalk.